Next: Inheritance, Previous: Properties, Up: `classdef` Classes [Contents][Index]

#### 34.6.3 Methods

All class methods must be defined within `methods` blocks. An exception to this rule is described at the end of this subsection. Those `methods` blocks can have additional attributes specifying the access rights or whether the methods are static, i.e., methods that can be called without creating an object of that class.

    classdef some_class
      methods
        function obj = some_class ()
          disp ("New instance created.");
        endfunction

        function disp (obj)
          disp ("Here is some_class.");
        endfunction
      endmethods

      methods (Access = mode)
        function r = func (obj, r)
          r = 2 * r;
        endfunction
      endmethods

      methods (Static = true)
        function c = circumference (radius)
          c = 2 * pi () .* radius;
        endfunction
      endmethods
    endclassdef

The constructor of the class is declared in the `methods` block and must have the same name as the class and exactly one output argument which is an object of its class.

It is also possible to overload built-in or inherited methods, like the `disp` function in the example above to tell Octave how objects of `some_class` should be displayed (see Class Methods).

In general, the first argument in a method definition is always the object that it is called from. Class methods can either be called by passing the object as the first argument to that method or by calling the object followed by a dot ("`.`") and the method’s name with subsequent arguments:

    >> obj = some_class ();
    New instance created.
    >> disp (obj);   # both are
    >> obj.disp ();  # equal

In `some_class`, the method `func` is defined within a `methods` block setting the `Access` attribute to mode, which is one of:

`public`

  The methods can be accessed from everywhere.

`private`

  The methods can only be accessed from other class methods. Subclasses of that class cannot access them.

`protected`

  The methods can only be accessed from other class methods and from subclasses of that class.

The default access for methods is `public`.

Finally, the method `circumference` is defined in a static `methods` block and can be used without creating an object of `some_class`. This is useful for methods, that do not depend on any class properties. The class name and the name of the static method, separated by a dot ("`.`"), call this static method. In contrast to non-static methods, the object is not passed as first argument even if called using an object of `some_class`.

    >> some_class.circumference (3)
    ⇒ ans =  18.850
    >> obj = some_class ();
    New instance created.
    >> obj.circumference (3)
    ⇒ ans =  18.850

Additionally, class methods can be defined as functions in a folder of the same name as the class prepended with the ‘`@`’ symbol (see Creating a Class). The main `classdef` file has to be stored in this class folder as well.

Next: Inheritance, Previous: Properties, Up: `classdef` Classes [Contents][Index]